Illumination apparatuses with light modules that have a wavelength conversion element in the form of a phosphor are known from the prior art.
LARP (laser activated remote phosphor) light sources, as they are referred to, have been known for a good while for video projection, and are based on the conversion of blue laser light into white useful light using phosphor converters. Depending on the application, white light is generated sequentially as a sequence of red, green and blue light using a dynamic or periodically moving LARP arrangement or is generated continuously by superposing blue and yellow light using a static or not periodically moving LARP arrangement.
In applications with great light demands, dynamic LARP arrangements with phosphor wheels are typically used, in which a more uniform distribution of the energy introduction takes place due to the rotational movement about the wheel axis. Rather than concentrating the entire excitation energy onto a single phosphor spot, as in static LARP arrangements, distribution is here effected over an extensive phosphor track. The rotation additionally facilitates the heat exchange with the ambient air.
For dynamic LARP arrangements, not just rotating phosphor apparatuses are known, but alternatively also linearly periodically moving or translationally oscillating phosphor apparatuses. A disadvantage here is that in the two turning points, a locally longer excitation duration occurs, among other things in connection with a typical increase in phosphor damage.
In static LARP arrangements, white light is frequently generated by only partially converting incident blue excitation light into yellow light, as a result of which the non-converted blue residual light that is scattered in the yellow phosphor can be superposed with the yellow conversion light to form white useful light. The LARP arrangements can here be designed both in reflection and transmission mode. In the reflection mode, blue, non-converted residual light and yellow conversion light are reflected by the phosphor apparatus, but is transmitted by it in the transmission mode. The advantage of this partial conversion method is in any case a continuous white light generation. The disadvantage, however, is that the color point of the white useful light is able to be set only with difficulty, because the ratio of the two color light components, blue and yellow, strongly depends on fluctuations in the manufacturing of the yellow phosphor layer (layer thickness variation, grain size distribution of the phosphor particles, density fluctuations of the phosphor particles in the surrounding matrix etc.). In addition, the blue/yellow ratio is fixedly specified and cannot be altered independently of one another.
On the other hand, full conversion is subject to far lower fluctuations, since here the radiated blue light is converted completely into yellow light by a suitable yellow phosphor. The white point of the resulting useful light can in this case be set relatively simply by adding purely blue light, e.g. from an additional blue LED or a blue laser diode.
Known in the prior art are phosphor wheels, in which white light is produced using full conversion from a change between yellow and blue light radiation components. Circular ring-shaped segments that convert excitation light or do not convert excitation light are provided herefor on the phosphor wheel. The problems with this type of sequential white-light generation are artefacts such as e.g. what is known as a color break, i.e. decomposition into the spectral components, from which the mixed light is composed, in a way that is visible to the human eye. This effect is especially great if the light generation is superposed by additional movements, such as is typical e.g. in the area of entertainment or effect lighting (e.g. Moving Heads, Sky Tracker). Previous attempts to solve this have sought to reduce the visibility of the color break by increasing the frequency of the change between the two color components (e.g. DE 102014221115 A1).